Method for opening a proprietary MAC protocol in a non-DOCSIS modem compatibly with a DOCSIS modem

ABSTRACT

A two way communication system is adapted for compatible inter-operation of a plurality of devices operating in accordance with a plurality of protocols. The communication system includes a first group of one or more remote devices that interface with a local host in accordance with a first protocol and a second group of one or more remote devices that interface wit the local host in accordance with a second protocol. The local host includes a protocol processor that identifies transmissions from the first and second groups of remote devices and routes transmissions from the first group of remote devices to a first processor operating in accordance with the first protocol and also routes transmissions from the second group of remote devices to a second processor operating in accordance with the second protocol.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional PatentApplication No. 60/171,912 filed Dec. 23, 1999 the content of which ishereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to broadband multimediadata distribution systems, and more particularly, to a method andapparatus for interfacing non-DOCSIS cable modems with DOCSIS compatiblecable modems.

BACKGROUND

[0003] Traditional dial-up modems provide online access through thepublic telephone network at up to 56 Kbps (equal to 56,000 bits persecond). A cable modem, on the other hand, provides users withhigh-speed Internet access through a cable television network. A cablemodem is capable of providing data rates as high as 56 Mbps, and is thussuitable for high speed Internet access, digital television (such aspay-per-view) and digital telephony.

[0004] The Data Over Cable Service Interface Specification (DOCSIS)protocol was developed to ensure that cable modem equipment built by avariety of manufacturers is compatible, as is the case with traditionaldial-up modems. However, DOCSIS compliant systems, as currently defined,do not efficiently transmit many types of data, such as, for example,voice.

[0005] Therefore, it would be desirable to provide a method andapparatus for operating a proprietary MAC protocol in customer premiseequipment, such as, for example, a cable modem, that overcomes thelimitations of the DOCSIS protocol, and interoperates with DOCSIScompatible cable modems resident on the same mixed network.

SUMMARY OF THE INVENTION

[0006] In one aspect of the present invention a method for networking acentral controller with a first group of one or more remote devicesoperating in accordance with a first protocol and a second group of oneor more remote devices operating in accordance with a second protocol,includes identifying transmissions from said first and second groups ofremote devices, routing transmissions from said first group of remotedevices to a first processor operating in accordance with the firstprotocol within the central controller, and routing transmissions fromthe second group of remote devices to a second processor operating inaccordance with the second protocol within the central controller.

[0007] In another aspect of the present invention a method fornetworking a cable modem termination system with a first group of one ormore cable modems operating in accordance with a proprietary protocoland a second group of one or more cable modems operating in accordancewith DOCSIS protocol, includes identifying transmissions from the firstgroup and second group of cable modems, routing transmissions from thefirst group of cable modems to a first processor that operates inaccordance with the proprietary protocol within the cable modemtermination system, and routing transmissions from the second group ofcable modems to a second processor that operates in accordance with theDOCSIS protocol within the cable modem termination system.

[0008] In a further aspect of the present invention, a two waycommunication system cable of compatible inter-operation of a pluralityof devices operating in accordance with a plurality of protocols. Thecommunication system includes a first group of one or more remotedevices that interface with a local host in accordance with a firstprotocol and a second group of one or more remote devices that interfacewit the local host in accordance with a second protocol. The local hostincludes a protocol processor that identifies transmissions from thefirst and second groups of remote devices and routes transmissions fromthe first group of remote devices to a first processor operating inaccordance with the first protocol and also routes transmissions fromthe second group of remote devices to a second processor operating inaccordance with the second protocol.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings where:

[0010]FIG. 1 is a schematic diagram of a hybrid fiber coaxial (HFC)network showing typical pathways for data transmission between theheadend (which contains the cable modem termination system) and aplurality of homes (each of which contain a cable modem);

[0011]FIG. 2 is a schematic diagram of a cable system having a cablemodem operating in accordance with a proprietary non-DOCSIS compatibleprotocol integrated with DOCSIS compatible cable modem system inaccordance with an exemplary embodiment of the present invention;

[0012]FIG. 3 is a system block diagram of an exemplary cable modemtermination system capable of supporting device operating in accordancewith two or more protocols in accordance with a preferred embodiment ofthe present invention;

[0013]FIG. 4a is a is a system block diagram of a DOCSIS comaptiblecable modem in accordance with a preferred embodiment of the presentinvention;

[0014]FIG. 4b is a system block diagram of a cable modem operating inaccordance with a proprietary protocol in accordance with a preferredembodiment of the present invention;

[0015]FIG. 5 is a flow diagram demonstrating the integration of anon-DOCSIS cable modem into a DOCSIS compatible cable modem system inaccordance with an exemplary embodiment of the present invention; and

[0016]FIG. 6 is graphical illustration of a MAC frame.

DETAILED DESCRIPTION OF THE INVENTION

[0017] An exemplary embodiment of the present invention provides amethod for operating a proprietary media access control (MAC) protocolin a non-DOCSIS cable modem. In the described exemplary embodiment, thenon-DOCSIS cable modem interoperates with DOCSIS compatible cable modemsresident on the same network. The DOCSIS protocol defines a series ofinterface specifications that standardize high speed packet basedcommunications on a cable television system. Compliance with the DOCSISprotocol ensures conforming hardware will interoperate to permittransparent bi-directional transfer of Internet Protocol (IP) traffic,as well as other traffic, between a cable headend and customer premiseequipment over an all-co-axial or hybrid-fiber/coax (HFC) cable network.In order to appreciate the advantages of the present invention, it willbe beneficial to describe the invention in the context of an exemplarybi-directional communication network, such as, for example, a HFCnetwork.

[0018] Referring now to FIG. 1, a HFC network facilitates thetransmission of data between a headend 12, which includes at least onecable modem termination system, and a number of homes 14, each of whichcontains a cable modem. As used herein, the CMTS is defined to includethat portion of a headend which facilitates communication with aplurality of cable modems. A typical cable modem termination systemincludes a burst receiver, a continuous transmitter and a medium accesscontrol (MAC) as disclosed in commonly owned U.S. patent applicationSer. No. 09/574,558, entitled “CABLE MODEM APPARATUS AND METHOD”, filedMay 19, 2000, the content of which is incorporated fully herein byreference. Such hybrid fiber coaxial networks are commonly utilized bycable providers to provide Internet access, cable television,pay-per-view and the like to subscribers.

[0019] Approximately 500 homes 14 are in electrical communication witheach node 16, 34 of the hybrid fiber coaxial network 10, typically viacoaxial cables 29, 30, 31. Amplifiers 15 facilitate the electricalconnection of the more distant homes 14 to the nodes 16, 34 by boostingthe electrical signals so as to desirably enhance the signal-to-noiseratio of such communications and by then transmitting the electricalsignals over coaxial cables 30, 31. Coaxial cable 29 electricallyinterconnects the homes 14 with the coaxial cables 30, 31, which extendbetween amplifiers 15 and nodes 16, 34. Each node 16, 34 is electricallyconnected to a hub 22, 24, typically via an optical fiber 28, 32. Thehubs 22, 24 are in communication with the headend 12, via optical fibers20, 26. Each hub is typically scapable of facilitating communicationwith approximately 20,000 homes 14.

[0020] The optical fibers 20, 26 extending intermediate the headend 12and each hub 22, 24 defines a fiber ring which is typically capable offacilitating communication between approximately 100,000 homes 14 andthe headend 12. The headend 12 may include video servers, satellitereceivers, video modulators, telephone switches and/or Internet routers18, as well as the cable modem termination system. The headend 12communicates via transmission line 13, that may be a T1 or T2 line, withthe Internet, other headends and/or any other desired device(s) ornetwork.

[0021] An exemplary embodiment of the present invention allows a singleCMTS to support on-line and off-line bidirectional communication betweennon-DOCSIS cable modems as well as between DOCSIS compatible cablemodems and a variety of far end data termination devices. An exemplarytopology is shown in FIG. 2, wherein a DOCSIS compatible cable modem 110provides an interface to HFC network 100 a for a fax machine 120 a,telephone 122 a and modem 124 a through a subscriber loop interfacecircuit (SLIC) 130 a. A non-DOCSIS cable modem 140 may also provide aninterface to the HFC network 100 a for a fax machine 120 b, a telephone122 b and a modem 124 b or other telephony, multi-media or computingdevices through a subscriber loop interface circuit (SLIC) 130 b. Alocal area network (LAN) 132 a, 132 b and a universal synchronous bus(USB) 134 a, 134 b may also be provided access to the HFC network 100 avia the DOCSIS and non-DOCSIS cable modems respectively.

[0022] The near-end HFC network 100 a is coupled to a CMTS line card 142in the headend 112. The CMTS line card 142 is coupled to a packet basednetwork router 144 to determine whether the communication will betransported via a far end HFC network 100 b, a far end PSTN network 150or the Internet. In the case of communications over a far end PSTNnetwork a PSTN gateway 152 provides an interface between a far end datatermination device 156 a and the PSTN network 150 connected to theheadend 112.

[0023] In the case of a far end HFC network 100 b, a cable modem, suchas, for example, a non-DOCSIS cable modem 140 b, provides an interfacebetween a far end data termination devices 156 b and the far end HFCnetwork 100 b connected to the headend 112. As those skilled in the artwill appreciate, the far end data termination devices 156 a and 156 bmay include a variety of telephony and data devices including atelephone, fax machine, and modem via a SLIC or audio processor, as wellas a LAN or USB.

[0024] The packet based network router 144 facilitates communicationbetween the near end data devices and off-line far end data terminatingdevices 156 a via a circuit switched network such as the public switchedtelephone network (PSTN) 150 and the PSTN gateway 152. Data terminationdevices include by way of example, analog and digital phones, ethernetphones, Internet Protocol phones, fax machines, data modems, cablemodems, interactive voice response systems, PBXs, key systems, and anyother conventional telephony devices known in the art. One skilled inthe art will appreciate that the described method of interfacing devicesoperating in accordance with different protocols is not limited to cablemodems on a HFC network. Rather the present invention may be used tointerface network gateways, set top boxes or other multimedia devices ona mixed network. Therefore, the described hybrid fiber coaxial network100 a is by way of example and not a limitation.

[0025] The multimedia cable network system (MCNS) DOCSIS radio frequencyinterface specification (SP-RFI-I02-971008) protocol specifies atime-division multiple access (TDMA) protocol for the upstreamtransmission of data packets from cable modems to a cable modemtermination system. In order to accomplish TDMA for upstreamcommunication, it is necessary to assign time slots within which cablemodems having a message to send to the cable modem termination systemare allowed to transmit. The CMTS assigns time slots in accordance withrequests that are placed in a request contention area in the upstreamdata path.

[0026] The CMTS responds to such requests from the cable modems with alogical message (MAP) that is broadcast to all of the cable modems on aparticular frequency channel. The MAP message specifies the upstreamframing structure, so as to provide individual time slots within whicheach cable modem may transmit. The MAP specifies which cable modems maytransmit, when they may transmit, and how, e.g., what modulation typethey may utilize to transmit.

[0027] Each cable modem is typically identified by one or more stationor service identifiers (SID). The MAP message specifies which SID orcable modem has control of upstream communications on a particularfrequency channel during each TDMA time slot. The MAP message alsospecifies the time at which the time slot begins and which intervalusage code or burst type is to be used. When the appropriate TDMA timeslot arrives (in time) a cable modem sends a burst of information, e.g.,a frame of voice or data, to the cable modem termination system.

[0028] In accordance with the DOCSIS time-division multiple accessprotocol, all devices (DOCSIS compatible or otherwise) operating on aDOCSIS network simultaneously receive MAP messages and broadcastrequests in the request contention region. Thus, to compatiblyinteroperate on a shared access network with DOCSIS compatible devices,a device operating according to a non-DOCSIS proprietary protocol mustnot interfere with the correct operation of the DOCSIS compatibledevices (e.g. cable modems and CMTS). In addition, communicationsbetween DOCSIS compatible devices preferably do not interfere with thecorrect operation of a device operating in accordance with a non-DOCSISprotocol.

[0029] Therefore, upstream communications on a mixed network thatoriginate from a device operating in accordance with a non-DOCSISprotocol are preferably distinguished from communications that originatefrom DOCSIS compatible devices. In operation, the CMTS may thereforeidentify and direct upstream non-DOCSIS transmissions to a compatibleprocessing unit in the CMTS and DOCSIS transmissions to a DOCSIScompatible processing unit in the CMTS. Further in the downstreamdirection, a CMTS is preferably able to communicate with a specificnon-DOCSIS device or all non-DOCSIS devices such that the communicationswill be ignored or discarded by the DOCSIS compatible devices.Similarly, downstream communications from the CMTS to DOCSIS compatibledevices are preferably ignored or discarded by the non-DOCSIS devices.

[0030] Referring to FIG. 3, cable modem termination system 142 includesa downstream modulator 200 for transmitting information such as, forexample voice, data, control or service messages to the cable modems andan upstream demodulator 202 for receiving communications from the cablemodems. Downstream modulator 200 may utilize, for example, 64 QAM or 256QAM in a frequency band in the range of 54 to 860 MHz to provide a datarate of up to 56 Mbps. Upstream demodulator 202 may use either QPSK or16 QAM, in a frequency range of 5 MHz to 42 MHz, to provide a data rateof up to 10 Mbps.

[0031] In the described exemplary CMTS, a MIPS core 240 in conjunctionwith its resident SRAM 250 and external memory 252, provide contentionresolution and scheduling functions to maximize the efficiency of thenetwork by adjusting the number of time slots in accordance with networktraffic patterns. The MIPS core also directs data traffic on bus 254.Furthermore, much of the data transmitted and received by the CMTSrequires extensive processing and formatting. The MIPS core 240 isresponsible for this processing and formatting. For example, the MIPScore manages the conversion of data between 64-QAM, QPSK, and thedigital packet format of the router interface. Further, MIPS core 240interprets management messages and provides basic database managementfunctions.

[0032] In the described exemplary embodiment, a protocol processor 210controls the interface between the physical layer (i.e. upstreamdemodulator and downstream modulator) and DOCSIS compatible andnon-DOCSIS compatible media access controllers 220 and 222 respectively.The protocol processor 210 identifies DOCSIS compatible upstream anddownstream communications and routes them to the DOCSIS MAC 220 forprocessing. Likewise the protocol processor 210 identifies non-DOCSIScompatible upstream and downstream communications and routes them to thenon-DOCSIS MAC 222 for processing.

[0033] Media access controllers (MAC) 220 and 222 encapsulate datareceived from a data network interface with the appropriate MAC addressof the cable modems on the system. Each cable modem on the system (notshown) has its own MAC address. Whenever a new cable modem is installed,its address is registered with the CMTS. The MAC address is necessary todistinguish upstream data from the cable modems since all the modemsshare a common upstream path, and so that the CMTS transmits downstreamcommunications to the proper cable modem. Thus, each data packet,regardless of protocol, is mapped to a particular MAC address.

[0034] A DOCSIS and non-DOCSIS cable modem are shown schematically inFIGS. 4a and 4 b respectively. The DOCSIS cable modem provides a DOCSIScompliant, single chip solution, as disclosed in commonly owned U.S.patent application Ser. No. 09/548,400, entitled “GATEWAY WITH VOICE”filed Apr. 13, 2000, the contents of which are incorporated herein byreference as if set forth in full. The DOCSIS cable modem 110 providesintegrated functions for communicating with far end devices via the CMTS(not shown). The non-DOCSIS cable modem 140 also provides integratedfunctions for communicating with far end data terminating devices.Non-DOCSIS cable modem 140 may operate in accordance with a non-DOCSIScompliant proprietary protocol as described in commonly owned U.S.patent application Ser. No. 09/427,792, entitled “SYSTEM AND METHOD FORMULTIPLEXING DATA FROM MULTIPLE SOURCES”, filed Oct. 27, 1999, thecontents of which are incorporated herein by reference as if set forthin full.

[0035] The DOCSIS cable modem 110 and the non-DOCSIS cable modem 140 mayutilize common PHY elements. For example, QPSK upstream modulators 300a, 300 b may be used to transmit data to a far end data terminatingdevice and QAM downstream demodulators 302 a, 302 b may receive datafrom the far end data terminating device via the CMTS. However, upstreammodulator 300 a and downstream demodulator 302 a in the DOCSIS cablemodem 110, interface with a DOCSIS MAC 304, while upstream modulator 300b and downstream demodulator 302 b in the non-DOCSIS cable modem 140interface with a non-DOCSIS MAC 310.

[0036] DOCSIS MAC 304 implements the downstream portions of the DOCSISprotocol. DOCSIS MAC extracts DOCSIS MAC frames from MPEG-2 frames,processes MAC headers, and filters and processes messages and data.Downstream data packets and message packets may then be placed in systemmemory 320 via an internal system bus (ISB). DOCSIS MAC 304 andnon-DOCSIS MAC 310 also control the upstream transmission parameters andencapsulate data received from peripheral signal sources with theappropriate header information including a service identifier(SID).

[0037] Cable modems 110 and 140 may accept information packets from aplurality of signal sources. For example, universal serial bus (USB)transceivers 322 a, 322 b and USB MACs 324 a, 324 b provide transparent,bi-directional IP traffic between devices operating on a USB such as forexample a PC workstation, server printer or other similar devices andthe far end data terminating device. Additionally, an I.E.E.E. 802.3compliant media independent interface (MII) 330 a, 330 b in conjunctionwith an Ethernet MAC 332 a, 332 b may also be included to providebi-directional data exchange between communications devices such as, forexample a number of PCs and or Ethernet phones and the far end dataterminating device.

[0038] In the described exemplary cable modems 110 and 140, a MIPS core360 a, 360 b in conjunction with resident SRAM 320 a, 320 b, manages theconversion of data between 64-QAM, QPSK, and the digital packet formatof the various peripheral devices. Further, MIPS core 360 interpretsmanagement messages and provides basic database management functions.

[0039] Cable modems 110, 140 may further include an internal audioprocessor 370 a,370 b with an analog front end 372 a,372 b thatinterface a voice processor 374 a,374 b with external subscriber lineinterface circuits (SLICS) 376 a,376 b for bi-directional exchange ofvoice signals. The voice processor 374 a,374 b includes an encoder anddecoder system (not shown) that may provide, for example, delaycompensation, voice encoding and decoding, DTMF generation anddetection, call progress tone generation and detection, comfort noisegeneration and lost frame recovery.

[0040] The audio processor 370 a,370 b may include programable elementsthat implement filters and other interface components for a plurality ofvoice channels. In the transmit mode the analog front end 372 a,372 baccepts an analog voice signal from SLIC 376 a, 376 b, digitizes thesignal and forwards the digitized signal to the audio processor 370.

[0041] The audio processor 370 a,370 b decimates the digitized signaland conditions the decimated signal to remove far end echos. As the nameimplies, echos in telephone systems is the return of the talker's voiceresulting from the operation of the hybrid with its two-four wireconversion. The audio processor 370 a,370 b can apply a fixedgain/attenuation to the conditioned signal and forwards the gainadjusted signal to the voice processor 374 a,374 b via the PCMinterface. In the receive mode the audio processor accepts a voicesignal via a PCM interface from the voice processor and applies a fixedgain/attenuation to the received signal. The gain adjusted signal isthen interpolated from 8 kHz to 96 kHz before being D/A converted forcommunication via a SLIC interface to a telephony device.

[0042] In one embodiment, non-DOCSIS MAC 310 may implement a proprietaryprotocol that provides for efficient multiplexing of voice and data forbi-directional communication over the HFC network. The non-DOCSIS cablemodem may evaluate the relative efficiency of data transmission for agiven grant region given the information packets currently waiting to betransmitted. The non-DOCSIS cable modem preferably evaluates therelationship between signal sources, the size of a packet relative tothe size of the grant region, transmission priorities, and otherknowledge regarding the data packets and the state of the network.Further, to maximize efficiency, the cable modem may concatenate orfragment information packets. In one embodiment, information packetsfrom any signal source may be concatenated with information from anyother, and transmitted within the same grant region. Further, thedescribed exemplary non-DOCSIS cable modem may transmit an informationpacket or fragment thereof in a grant region assigned to differentinformation packet.

[0043] Referring to FIG. 5, the CMTS identifies and processes upstreamcommunications from, and downstream communications to, the DOCSIS andnon-DOCSIS cable modems. In one embodiment, service identifiers (SIDs)in the frame header of upstream communications may in part serve toidentify DOCSIS compatible and non-DOCSIS compatible devices. A MACframe is the basic unit of transfer between the MAC sublayers at theCMTS and the cable modems. The same basic structure is used in both theupstream and downstream directions. A MAC frame comprises a MAC headerthat identifies the content of the MAC frame and an optional packet dataunit (PDU).

[0044] MAC headers comply with the header format illustrated in FIG. 6.Generally the MAC headers include a frame control field (FC) 500 thatidentifies the type of MAC header, as well as a MAC control field 510,an optional extended header field 520 and a header check sequence 530 toensure the integrity of the MAC header. Broadly speaking there are twotypes of frames transmitted on the upstream channel by the cable modemsto the CMTS. Namely, contention minislot requests that include one ormore SIDs 540 in the header structure and all other types of frames thattypically do not include a service identifier but rather include thelength 550 of the MAC frame.

[0045] In an exemplary embodiment of the present invention, each deviceon the network is initially assigned a primary service identifier(PSID), that serves to identify the traffic characteristics andscheduling requirements for that cable modem. In addition, each deviceis also assigned additional SIDs identifying the device as being DOCSIScompatible or non-DOCSIS compatible. The DOCSIS and non-DOCSIS MACs ofthe cable modems embed the additional SIDs in each contention minislotframe. The protocol processor in the CMTS may then identify requestsfrom DOCSIS and non-DOCSIS compatible devices in accordance with theembedded SIDs.

[0046] Referring back to FIG. 5, in operation, the CMTS may thereforedirect requests in the contention request region from devices havingnon-DOCSIS compatible SIDs to a corresponding non-DOCSIS processorwithin the CMTS 410. Similarly, the CMTS may direct requests fromdevices having DOCSIS compatible SIDs to a corresponding DOCSISprocessor within the CMTS 420. The CMTS may then appropriately respondto such requests with a grant of bandwidth during which the cable modemsmay transmit 424. In addition, in the described exemplary embodiment,collisions between two or more packets at the CMTS are ignored having noeffect on CMTS processing.

[0047] However, in the grant region cable modems transmit transportframes on the upstream channel that do not have a SID embedded in theframe header. Rather, the SID field is replaced by a field identifyingthe length of the packet data unit. Therefore, the CMTS can not directlyidentify the cable modem that transmitted a particular frame byexamining that frame. However, upstream transmissions that do not have aSID field are transmitted in accordance with a minislot assignment fromthe CMTS. The scheduler in the MIPS core of the CMTS therefore knows apriori which device transmitted each frame in a particular set ofminislots. Thus, the CMTS may also identify upstream communications inthe grant region transmitted by both DOCSIS compatible and noncompatible devices.

[0048] In operation, the CMTS may therefore direct upstreamcommunications in the grant region from non-DOCSIS compatible devices toa corresponding non-DOCSIS processor within the CMTS. Similarly, theCMTS may direct upstream communications in the grant region from DOCSIScompatible devices to a corresponding DOCSIS processor within the CMTS.The appropriate processor within the CMTS therefore processes upstreamcommunications in the grant region and forwards those communications tothe addressed far end device 424. The CMTS may therefore insulate eachupstream communication from potential interference from a non-compatibledevice. The grant region of the upstream allocated to non-DOCSIS devicesis not mapped by the DOCSIS system mapper.

[0049] In the downstream direction the DOCSIS protocol requires thecommunication of a single broadcast messages, such as, for example, MAPmessages, to each device on the network. To comply with this requirementa CMTS in a system having groups of devices operating in accordance withtwo or more different protocols may utilize the DOCSIS multicastmechanism to communicate with each device in a particular group. Forexample, the CMTS may first create a multicast group for the cablemodems operating in accordance with each different protocol 440. TheCMTS may then communicate with a group of devices operating inaccordance with a particular protocol by transmitting a packet using amulticast group 450 that includes each device within that group.

[0050] In the described exemplary embodiment, multicast packetsaddressed to non-DOCSIS compatible devices conform with the requirementsfor a DOCSIS multicast packet so as not to produce an error condition ina DOCSIS compatible device. Multicast communications addressed tonon-DOCSIS compatible groups however, are ignored by DOCSIS compatibledevices since they are not part of the multicast group. Similarly,multicast packets addressed to a group of DOCSIS compatible devices willbe ignored by non-DOCSIS devices that are not part of the multicastgroup.

[0051] In the described exemplary embodiment, downstream communicationswith a group of non-DOCSIS compatible devices may be done in the payloadof the multicast frame. For example, control information intended for agroup of non-DOCSIS devices may be transmitted to that group in thepayload of a multicast frame. Similarly, the payload of a non-DOCSISmulticast frame may be used to transmit MAP messages downstream toallocate upstream capacity to devices within the non-DOCSIS compatiblegroup.

[0052] Further, the CMTS may correlate the destination address of farend communications with the protocol of the addressed device 460. TheCMTS may therefore, route far end communications to the appropriateprocessor within the CMTS for processing in accordance with the protocolof the addressed device. The CMTS may then forward the processeddownstream communication having a unicast MAC address to the downstreammodulator for communication to the individual addressed device 470.Downstream unicast communications are therefore ignored by all otherdevices. Thus, the CMTS may also communicate downstream with individualdevices operating in accordance with a non-DOCSIS protocol withoutinterfering with the operation of DOCSIS compatible devices on the samemixed network. Therefore, a bi-directional communication networkoperating in accordance with the present invention may support devicesoperating in accordance with a plurality of protocols for efficientutilization of network bandwidth.

[0053] Although a preferred embodiment of the present invention has beendescribed, it should not be construed to limit the scope of the appendedclaims. Those skilled in the art will understand that variousmodifications may be made to the described embodiment. Moreover, tothose skilled in the various arts, the invention itself herein willsuggest solutions to other tasks and adaptations for other applications.It is therefore desired that the present embodiments be considered inall respects as illustrative and not restrictive, reference being madeto the appended claims rather than the foregoing description to indicatethe scope of the invention.

What is claimed is:
 1. A method for networking a central controller with a first group of one or more remote devices operating in accordance with a first protocol and a second group of one or more remote devices operating in accordance with a second protocol, comprising: identifying transmissions from said first group and said second group of remote devices; routing transmissions from said first group of remote devices to a first processor operating in accordance with said first protocol within said central controller; and routing transmissions from said second group of remote devices to a second processor operating in accordance with said second protocol within said central controller.
 2. The method of claim 1 further comprising embedding a first identifier in transmissions from said first group of remote devices and embedding a second identifier in transmissions from said second group of remote devices, wherein transmission from said first and second groups of remote devices are identified in accordance with said first and second identifiers.
 3. The method of claim 2 wherein said transmissions from said first and second group of remote devices comprise bandwidth requests transmitted in a request contention area.
 4. The method of claim 3 further comprising transmitting bandwidth grants to said first and second group of remote devices in response to requests for bandwidth.
 5. The method of claim 1 further comprising assigning one or more time slots during which said first group and second group of remote devices may transmit information to said central controller and wherein said central controller identifies transmission from said first group and second group of remote devices in accordance with said assigned time slots.
 6. The method of claim 1 further comprising creating a first multicast group comprising said first group of remote devices, creating a second multicast group comprising said second group of remote devices and transmitting group messages from said central controller to said first group and second group of remote devices in accordance with said first and second multicast groups.
 7. The method of claim 1 further comprising receiving communications for said first group and second group of remote devices in accordance with addresses of said first and second remote devices, routing communications for said first group of remote devices to said first processor within said central controller, routing communications for said second group of remote devices to said second processor within said central controller and transmitting processed communications to addressed remote devices.
 8. A method for networking a cable modem termination system with a first group of one or more cable modems operating in accordance with a proprietary protocol and a second group of one or more cable modems operating in accordance with DOCSIS protocol, comprising: identifying transmissions from said first group and second group of cable modems; routing transmissions from said first group of cable modems to a first processor that operates in accordance with said proprietary protocol within said cable modem termination system; and routing transmissions from said second group of cable modems to a second processor that operates in accordance with the DOCSIS protocol within said cable modem termination system.
 9. The method of claim 8 further comprising embedding a first identifier in transmissions from said first group of cable modems and embedding a second identifier in transmissions from said second group of cable modems, wherein transmission from said first group and second group of cable modems are identified in accordance with said first and second identifiers.
 10. The method of claim 9 wherein said transmissions from said first and second group of cable modems comprise bandwidth requests transmitted in a request contention area.
 11. The method of claim 10 further comprising transmitting bandwidth grants to said first and second group of cable modems in response to said requests for bandwidth.
 12. The method of claim 8 further comprising assigning one or more time slots during which said first group and second group of cable modems may transmit information to said cable modem termination system and wherein said cable modem termination system identifies transmission from said first group and second group of cable modems in accordance with said assigned timeslots.
 13. The method of claim 8 further comprising creating a first multicast group comprising said first group of cable modems, creating a second multicast group comprising said second group of cable modems and transmitting group messages from said cable modem termination system to said first group and second group of cable modems in accordance with said first and second multicast groups.
 14. The method of claim 8 further comprising receiving communications for said first group and second group of cable modems in accordance with addresses of said first group and second group of cable modems, routing communications for said first group of cable modems to said first processor within said cable modem termination system, routing communications for said second group of cable modems to said second processor within said cable modem termination system and transmitting processed communications to addressed cable modems.
 15. A two way communication system comprising: a plurality of remote devices wherein a first group of one or more remote devices communicate with a local host in accordance with a first protocol and a second group of one or more remote devices communicate with said local host in accordance with a second protocol, wherein said local host comprises a protocol processor for identifying transmissions from said first and second groups of remote devices, and wherein said protocol processor routes transmissions from said first group of remote device to a first processor operating in accordance with the first protocol and wherein said protocol processor routes transmissions from said second group of remote devices to a second processor operating in accordance with the second protocol.
 16. The two way communication system of claim 15 wherein said local host further comprises a central processor for scheduling transmission from said first and second group of remote devices.
 17. The two way communication system of claim 15 wherein said local host further comprises an upstream demodulator for receiving transmission from said first and second group of remote devices and a downstream modulator for transmitting information to said first and second group of remote devices.
 18. The two way communication system of claim 17 wherein each of said remote devices comprise a downstream demodulator for receiving transmission from said local host and an upstream modulator for transmitting information to said local host.
 19. The two way communication system of claim 18 wherein each of said remote devices further comprise a media access controller for embedding service identifiers in each upstream bandwidth request, wherein said media access controller embeds a first service identifier for remote devices that operate in accordance with said first protocol and a second service identifier for remote devices that operate in accordance with said second protocol.
 20. A cable television system, comprising: a plurality of cable modems wherein a first group of one or more cable modems communicate with a cable modem termination system in accordance with a proprietary protocol and a second group of one or more cable modems communicate with said cable modem termination system in accordance with DOCSIS protocol, wherein said cable modem termination system comprises a protocol processor for identifying transmissions from said first and second groups of cable modems, and wherein said protocol processor routes transmissions from said first group of cable modems to a first processor operating in accordance with the proprietary protocol and wherein said protocol processor routes transmissions from said second group of cable modems to a second processor operating in accordance with the DOCSIS protocol.
 21. The cable television system of claim 20 wherein said transmissions from said first and second groups of cable modems comprise bandwidth requests transmitted in a request contention area.
 22. The cable television system of claim 21 wherein said cable modem termination system further comprises a central processor for scheduling transmission from said first and second group of cable modems in response to said bandwidth requests.
 23. The cable television system of claim 20 wherein said cable modem termination system further comprises an upstream demodulator for receiving transmission from said first and second group of cable modems and a downstream modulator for transmitting information to said first and second group of cable modems.
 24. The cable television system of claim 23 wherein each of said cable modems comprise a downstream demodulator for receiving transmission from said cable modem termination system and an upstream modulator for transmitting information to said cable modem termination system.
 25. The cable television system of claim 24 wherein each of said cable modems further comprise a media access controller for embedding service identifiers in each upstream bandwidth request, wherein said media access controller embeds a first service identifier for cable modems that operate in accordance with said proprietary protocol and a second service identifier for cable modems that operate in accordance with said DOCSIS protocol. 